1 Topic by timberwolf21

  • timberwolf21
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Topic: Help: Hotend Temp Skyrockets Intermittently

I've had an odd issue in the last month with my Solidoodle 2nd Gen; at first I thought it was user error, a typo or some such that I had done without noticing. But after further investigation something else is definitely causing an issue.

My Printer will spontaneously allow the Hotend to skyrocket in temperature despite being set to operate at 195C. The first time this happened the unit reached 360C and the Hotend, and the 5W 5.6ohm resistor were FUBAR. I had dismissed this initially as having somehow been a user related error with a typo or keyboard stroke that had gone unnoticed.

This morning however I received my new Hotend Assembly from Solidoodle and installed the replacement parts and began calibrating everything for good measure. While the Hotend was OFF it silently spiked to 210C before I killed the power while I was leveling my print-bed. I ran some more tests and the issue occurred again while the unit was idle and the hotend was 'off'. For the sake of ruling out drivers, or software. I decided to uninstall Repetier Host, download the latest version; go into System and remove the drivers manually for Port COM3, cleared my registry and installed the latest version of Reptier Host and a fresh set of drivers. The issue occurred again while running an Auto-PID but this time, I caught the bugger red handed.

Whats more dangerous is emergency Stop and User Controls for the printer do not stop the Hotend from continuing to scale in temperature. Even the Auto-cutoff safety (M143) I put at 215C doesn't work even though it triggers. Only pulling the power seems to resolve the issue.

I'm really stumped on this one, and it's too dangerous to operate if I can't resolve the issue. The wiring in back looks okay, everything is seated firmly on the board, wires are not frayed or damaged. (My unit is not even a year old yet and hasn't seen heavy duty) The wiring for my hotend is correct since it accurately reports the temperatures regardless of the fact it seems hellbent on melting down.

Any help would be much appreciated!

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2 Reply by ronsii

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Re: Help: Hotend Temp Skyrockets Intermittently

sounds like a problem with the mainboard or the mosfet on the board... could also be something shorting on the back of the mainboard... are you comfortable with taking the board off of the printer?

3 Reply by timberwolf21

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Re: Help: Hotend Temp Skyrockets Intermittently

I was afraid that might be it. I am ready to say it's my board or a short somewhere. Yea I'm fine with taking the board off the printer. I'm just unfamiliar with how to troubleshoot these boards. At a glance I don't see any signs of damage, but I haven't done any real tests with the unit.

4 Reply by ronsii

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Re: Help: Hotend Temp Skyrockets Intermittently

I have seen bits of wire clippings getting stuck to the backside of pc boards... in fact I remember someone on this forum had a similar problem where a piece of wire trimmed from the board was stuck and one day it loosened and shorted something out!!! can't remember who it was but I am sure he will chime in if he see's this.

Just be careful when removing the board they have washers and spacers that are a tricky to get back in place and you don't want one to slip when putting it back together and then cause other problems.

The more I think about it from your description of the happenings it almost has to be a physical problem like something shorting power through the mosfet that controls the hotend.

5 Reply by ronsii

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Re: Help: Hotend Temp Skyrockets Intermittently

Oh, forgot to ask how long have you had the printer? and which mainboard is it? also have you contacted SD about the problem? this sounds like something they would/should be interested in.

6 Reply by timberwolf21 (edited by timberwolf21 2013-12-31 04:03:26)

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Re: Help: Hotend Temp Skyrockets Intermittently

I did send a support ticket requesting assistance with this, but they haven't gotten back to me yet. My printer will be a year old at the end of January. The board is a Rev 1.30 || W/O 110128-2 Serial 1250002316 according to the sticker on the chip set.

I did some checks with my multimeter and all my results mismatched what the Solidoodle troubleshoot Wiki had suggested my Ohm values should be reading at. But I'm wondering if it might just be my meter, as my Printing Bed runs flawlessly even now, and it's reading was also off the suggested values.

Hotend Resistor reads 7.0 Ohms
Hotend Thermistor reads 98k Ohmz

Print-Bed Line to Board reads 3.2 Ohms
HotEnd Line to Board reads 7.2 Ohms

This unit has made about three dozen prints in its lifetime, none above 3 hour jobs. Has its own safe workstation to operate from free of foreign matter and debris. Is connected to a Back-UPS 350 surge protector. The history of this unit other than the Hot-end melting as a result of this current issue. (Really just the Resistor fried after I dissected the unit for spare parts. The nozzle didn't even jam despite plastic oozing out of the original J-Nozzle assembly) My unit has been flawless and trouble free of any issues apart from minor calibration tweaks here and there. So this recent turn of events is quite unexpected.

If there are any other tests I can do on the power supply, or board please link me a reference or provide some instruction and ill attempt it. Also after looking at the board I dont see any stray wiring that may be causing the issue.

7 Reply by timberwolf21 (edited by timberwolf21 2013-12-31 04:45:04)

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Re: Help: Hotend Temp Skyrockets Intermittently

So I tried reseating the wiring Harness and re-plugging and triple checking connections from board to hotend and did another PID calibration at 195C that passed without an issue. However during a closely monitored test print I observed something interesting.

Every time power was supplied to the Hot-end to bring the temperature back into operating range, it would slowly begin to fluctuate more and more until it hit my MAXTEMP threshold and ultimately overheat, before pulling the plug on the unit. Now this behavior was more logical than the other less expected behavior with the whole it turns itself on and immediately begins to overheat even when I haven't turned the Extruder on. But hopefully this is a more solid clue to the issue at hand.

Any thoughts?

(Image is the Temperature graph leading up to the failure)

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8 Reply by Hazer

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Re: Help: Hotend Temp Skyrockets Intermittently

Its pretty obvious from your temperature log that at some point the extrusion output from the MCU turns off, but the heater keeps going. The MOSFET is your main culprit. You can confirm this with your multimeter.

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9 Reply by timberwolf21

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Re: Help: Hotend Temp Skyrockets Intermittently

Thanks for the tip Hazer, I suspect you are right.

Solidoodle contacted me this morning and after a series of tests to rule out common issues they've asked me to send the unit back to them for repair, so I guess that's what's going to happen. Looks like I'll be without a printer for a while, but oh well. Certainly better than watching it melt down or being paranoid about when it will happen again.

They were quick to respond to my support request I'm impressed. smile

Thanks for the help everyone, if I get a detailed reason as to the cause I'll leave a note here, I can't imagine I'm the only one with this issue, but it's certainly not common.